European debt worries send U.S. stocks lower

APTraders on the floor of the New York Stock Exchange.NEW YORK -- U.S. stocks tumbled early today hit by heightened concerns about Europe as violence erupted in Greece and a possible downgrade loomed over Portugal's debt.

Today's early drop came after Moody's Investors Service placed Portugal's government bond rating under review for a possible downgrade based on the deterioration of the country's public finances and its long-term economic challenges. Meanwhile in Greece, a nationwide strike spiraled into violence. Three people were killed after a fire broke out at riots near an Athens bank.

The worries sent the euro crashing to new one-year low as the dollar soared. The U.S. Dollar Index, which represents the U.S. currency against a basket of six others, gained 1.1 percent. As investors fled from riskier assets, crude-oil prices tumbled to below $80 a barrel. Gold futures also sank.

Investors said a potential downgrade to Portugal could impact portfolio managers obligated to pull out of assets downgraded by two of the three major credit rating agencies.

"Now it's musical chairs and do I want to be the one without a chair when this thing starts to go bad?" asked Bob Tull, chief operating officer at Old Mutual Global Index Trackers. "I don't think anyone wants to be in that position anymore." -MarketWatch